Date: Fri, 22 Mar 2024 18:40:14 GMT From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 806e51f81dba - stable/13 - if_wg: use proper barriers around pkt->p_state Message-ID: <202403221840.42MIeEKr019810@gitrepo.freebsd.org>
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The branch stable/13 has been updated by kevans: URL: https://cgit.FreeBSD.org/src/commit/?id=806e51f81dbae21feb6e7ddd95d2ed2a28b04f8f commit 806e51f81dbae21feb6e7ddd95d2ed2a28b04f8f Author: Kyle Evans <kevans@FreeBSD.org> AuthorDate: 2024-03-15 01:19:18 +0000 Commit: Kyle Evans <kevans@FreeBSD.org> CommitDate: 2024-03-22 15:21:42 +0000 if_wg: use proper barriers around pkt->p_state Without appropriate load-synchronization to pair with store barriers in wg_encrypt() and wg_decrypt(), the compiler and hardware are often allowed to reorder these loads in wg_deliver_out() and wg_deliver_in() such that we end up with a garbage or intermediate mbuf that we try to pass on. The issue is particularly prevalent with the weaker memory models of !x86 platforms. Switch from the big-hammer wmb() to more explicit acq/rel atomics to both make it obvious what we're syncing up with, and to avoid somewhat hefty fences on platforms that don't necessarily need this. With this patch, my dual-iperf3 reproducer is dramatically more stable than it is without on aarch64. PR: 264115 Reviewed by: andrew, zlei (cherry picked from commit 3705d679a6344c957cae7a1b6372a8bfb8c44f0e) --- sys/dev/wg/if_wg.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/sys/dev/wg/if_wg.c b/sys/dev/wg/if_wg.c index 89b5e52b7b2b..6638524301b8 100644 --- a/sys/dev/wg/if_wg.c +++ b/sys/dev/wg/if_wg.c @@ -1519,8 +1519,7 @@ wg_encrypt(struct wg_softc *sc, struct wg_packet *pkt) state = WG_PACKET_CRYPTED; out: pkt->p_mbuf = m; - wmb(); - pkt->p_state = state; + atomic_store_rel_int(&pkt->p_state, state); GROUPTASK_ENQUEUE(&peer->p_send); noise_remote_put(remote); } @@ -1592,8 +1591,7 @@ wg_decrypt(struct wg_softc *sc, struct wg_packet *pkt) state = WG_PACKET_CRYPTED; out: pkt->p_mbuf = m; - wmb(); - pkt->p_state = state; + atomic_store_rel_int(&pkt->p_state, state); GROUPTASK_ENQUEUE(&peer->p_recv); noise_remote_put(remote); } @@ -1649,7 +1647,7 @@ wg_deliver_out(struct wg_peer *peer) wg_peer_get_endpoint(peer, &endpoint); while ((pkt = wg_queue_dequeue_serial(&peer->p_encrypt_serial)) != NULL) { - if (pkt->p_state != WG_PACKET_CRYPTED) + if (atomic_load_acq_int(&pkt->p_state) != WG_PACKET_CRYPTED) goto error; m = pkt->p_mbuf; @@ -1691,7 +1689,7 @@ wg_deliver_in(struct wg_peer *peer) struct epoch_tracker et; while ((pkt = wg_queue_dequeue_serial(&peer->p_decrypt_serial)) != NULL) { - if (pkt->p_state != WG_PACKET_CRYPTED) + if (atomic_load_acq_int(&pkt->p_state) != WG_PACKET_CRYPTED) goto error; m = pkt->p_mbuf;
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